[Feature Request] Add `docfx --info` command to show user's environment information

**Is your feature request related to a problem? Please describe.**
It might be useful to support `docfx --info` command similar to `dotnet --info`

**Background**
It's hard to distinguish user's environment from reported issue.

For example
- `docfx` command is not resolved to expected path (e.g. overridden by higher priority `PATH` that installed with chocolately)
- Can't distinguish running docfx is NuGet distributed version or Self Contained version. (and installed by chocolately/homebrew)
- NuGet feed sources is customized and `nuget.org` source is disabled.
- `DOTNET_ROOT` is customized for docfx. (e.g. docfx Installed by homebrew)

**Describe the solution you'd like**
Add `docfx --info` command and update `ISSUE_TEMPLATE`.

**Example of information that required for diagnostics**
- `dotnet --info` command results (List of .NET SDKs/ `global.json` is used or not)
- `docfx --version` information
- `docfx template list` result and it's physical paths.
- `templates` build version. (Currently set `1.0,0` and this information is not included to templates dir)
- `dotnet nuget list source` information
- docfx exe location (AppContext.BasePath)
- docfx is `.NET tool` or `SelfContained` or build from source.
- RuntimeEnvironmentinformation
- RuntimeEnvironment.GetRuntimeDirectory
- RuntimeInformation.FrameworkDescription
- RuntimeInformation.OSArchitecture
- RuntimeInformation.OSDescription
- RuntimeInformation.ProcessArchitecture (Required to check docfx running on ARM64 CPU with X64 emulation mode)
- Additionary `docfx.json` settings and folder structure tree.